Process for the manufacture of alpha-naphthol



Patented Sept. 27, 1932 UNITED STATES PATENT OFFICE mIIIL LAAGE, 0F 'UERDINGEN,

AKTIENGESELLS CHAFT,

TO I. G. FARBENINDUSTRIE PROCESS FOR THE MANUFACTURE OF a-NAPI-ITHOL No Drawing. Application filed April 7, 1930, Serial No. 442,445, and in Germany April 10,

The invention relates to an improved process of preparing l-hydroxynaphthalene (anaphthol).

I have found that a-keto-tetrahydronaphthalene, which is represented by the formula and may be regarded as tautomeric with 3-4- dihydro-l-hydroxynaphthalene \l on U 011/ may easily be converted into oz-IlitPlltl'lOl by treating it with sulphur, according to the equation 1o 1o S CIOHSO zs,

the amount of sulphur not exceeding the molar amount calculated upon the amount of the a-ketotetrahydronaphthalene. In carrying out my invention, I heat the a-keto-tetrahydronaphthalene together with sulphur to an elevated temperature until the evolution of hydrogen sulphide ceases. I prefor to take the a-keto-tetrahydronaphthalene in some excess over the amount calculated stoiohiometrically, the unchanged portion serving as solvent. The dehydrogenating action of the sulphur may be promoted by the addition of selenium, tellurium, arsenic, antimony or a heavy metal, such as copper, silver, zinc, tin, preferably in a finely divided state, or an oxide or sulphide of such a metal.

Furthermore, organic catalysts of the kind used as accelerators in rubber curing processes, for example, diphenylguanidine, mercaptobenzothiazole, hexamethylene-tetramine and other condensation products of aldehydes and amino compounds may be added.

The invention is illustrated by the foll0wing example, without being restricted to it: A mixture of 160 parts by weight of oz-kGlZO- tetrahvdronaphthalene and 32- parts of sulknown means or reconverted into sulphur, for

instance, by moderate catalytic oxidation. WVhen no more hydrogen sulphide is evolved,

the a-naphthol formed is separated by fractional distillation under dimlnished pressure,

the excess or" a-keto-tetrahydronaphthalene being recovered from the first runnings. The a-naphthol may be further purified b crystallization or by'dissolving it in ilute 1' caustic alkali solution and precipitating by means of an acid. The yield is about 130 parts by weight of a-naphthol. 7

If the above named mixture is treated in V the same manner after .adding 1 part of selenium or 1 part of arsenious oxide or 1 part of finely divided tin or 1 3 parts of diphenylguanidine, a yield of a-naphthol approximating the theoretical value may be obtained.

I claim:

- 1. The new process which comprises heating a-ketotetrahydronaphthalene with sulphur, the amount of sulphur not exceeding the molar amount calculated upon the amount of the a-ketotetrahydronaphthalene.

2. The new process which comprises heating a-ketotetrahydronaphthalene with sulphur to a temperature of about 200 (1, the amount of sulphur not exceeding the molar amount calculated upon the amount of the a-ketotetrahydronaphthalene.

3. The new process which comprises heating wketot-etrahydronaphthalene with sulphur to a temperature of about 200 C., in the presence of an organic catalyst selected from the group consisting of diphenylguanidine, mercaptobenzothiazole, hexamethylenetetramine and other condensation products of aldehydes and amino compounds.

In testimony whereof, I afiix my signature.

EMILLAAGE.

part of zino oxide and 

